During a time of war, a plane crashes on an island with the only survivors being a group of preadolescent boys. One of the boys, Ralph, is quickly elected as their chief as they attempt to survive as a unit until rescues. Ralph sets up some ground rules including, whoever has the conch has the turn to speak, to keep a fire lit at all times, and to have fun.
The group natural splits into a hunting group and a shelter building group. The order of the boys society start to deteriorate when little attention is paid to survival and more is paid to the rumored beast on the island. One day a ship passes near the island but does not see the boys' existence because they have let the fire go out. Ralph is angered and almost retreats his position but is talked out of it by his friend piggy.
Shortly after, a fighter pilot's body is washed up to shore after an arial battle. Mistaken for the beast, Ralph, Jack - the up and coming leader against Ralph -, and Roger decide to go looking for it. When Ralph turns back before the others, Jack attempts to turn the group against Ralph. When they refuse he starts his own "tribe" on the other side of the island where they start to paint their faces and take part in bizarre rituals. While the boys were partaking one of these rituals they mistake another boy coming to tell them the "beast" was really the pilot, as the beast itself and is killed.
When the tribe decides to possess piggys glasses for a fire and are confronted by Piggy, Ralph, Sam and Eric, Sam and Eric are taken captive, piggy is killed with a dropped boulder and a man hunt is set out for Ralph. During the hunt the island is set in flames and after a long close chase Ralph stumbles upon a rescue crew worker who's team had noticed the flames. Reassuming their innocence and assessing what they had been through the boys burst into tears.